Hi
I wonder why there are no any driver circuits in the web, using 2sc5200/2sa1943 transistors for driving motors. It gives up to 15A collector current with higher hfe than 3055, and it is chip!!! What is the catch?
Regards
How about because for most purposes MOSFETs work a lot better?
Steve
slipstick:
How about because for most purposes MOSFETs work a lot better?Steve
I am talking about those cases in which you can't avoid transistor. For example cases in which the body diode is an issue. Or cases in which cost is a matter. What is wrong with 2sc5200? I have seen motors using 3055 or BD911 but 5200 looks a better choice. Or not? What is your opinion?
Bipolar transistors for power electronics is much less efficient than MOSFETs, its not used any more (thyristors apart), the trend is to SiC and GaN MOSFETs and away from silicon even.
MOSFET efficiencies can be > 99%, MOSFET switching speeds are 100kHz and up these days, a bipolar
switching device would be pushing it at 20kHz due to the sluggish turn-off behaviour. Higher switching
speed = smaller inductors and capacitors, less board area and less cost.
For high voltage power conversion IGBT's take over from MOSFETs, they are a kind of MOSFET/BJT
hybrid better suited to high voltage (more rugged to voltage transients). SiC MOSFETs are likely to
take over from IGBTs to some extent from what I read.
The body diode an issue? its actually a boon for power conversion and is sometimes bolstered with
parallel schottky diodes to improve performance. IGBT circuits have to have diodes added specifically
because an IGBT doesn't have a body diode.
Its only linear amplification where BJTs stand out as a good fit (although secondary breakdown is
a big achillies heel for high power amplifiers).
I might use those if I ever wanted to make a high power audio amp but I can't think of any case where I'd use them for motor drive. As for 2N3055s, they were fine when I was using them 40 odd years ago but I'm quite surprised to see they still exist.
Steve
They were the only high current silicon transistor once, that's why they were popular, not because they
are actually very good (!) - for instance 3A in for 15A out is pretty horrible, and its not much faster
than a darlington of the same period.
If you want a good audio amp transistor these days the comp. pair NJW3281G/NJW1302G are a
good choice, very little gain droop at high current, more than 10 times the bandwidth of the 2N3055/2N2955
pair, much higher max voltage.
Of course it is class-D amplification, you're back to switching devices and MOSFET rule.